Screw conveyers are used for transporting a wide variety of materials in many diverse industries, including mining, manufacturing, agriculture and food processing. The material to be transported is introduced into a tube or channel containing the screw conveyer, which consists of a helicoid flighting attached for rotation by a driven shaft.
In the case of food handling or processing systems, since the food products are in intimate contact with the flighting and shaft of the conveyer, sanitation and health regulations require that the conveyers be capable of thorough cleaning on a periodic basis, and that disassembly and reassembly operations, if any, that are necessary for cleaning be kept to a minimum in terms of the time, tools and personnel skills required.
Screw conveyers for food handling and processing applications are generally made of stainless steel, with the stainless steel flighting permanently attached to the center drive shaft. The most common method of construction consists of welding the flighting in place along the inner edge thereof where it is in contact with the drive shaft. However, this type of construction is subject to several problems. The welding at the intersection of the flighting and the shaft has a pitted or roughened surface which provides many extremely small recesses in which food product and bacteria can lodge. Cleaning this weld area can be very difficult due to the irregular and small size of the recesses, and their location at the base of the flighting along the helical intersection with the shaft, which makes it somewhat inaccessible for brushing and the like. One solution is to grind and polish the welds to a smooth surface during the manufacturing process, but this is difficult and expensive because of the helical configuration which does not lend itself easily to conventional machining processes. Another solution has been to coat the weld or entire assembly in a protective coating, such as epoxy. However, the coating materials themselves are subject to physical or chemical erosion over a period of time and may chip or peel away creating cleaning problems referred to above.
Another way to avoid the above-mentioned problems associated with the welds is to have the flighting held to the shaft by means other than welding. However, various types of brackets, screws, slots, rivets, etc. may themselves contribute to cleaning problems in terms of small, inaccessible recesses, edges and the like.
Another way to solve the cleaning problems is to make the flighting removable from the shaft to permit access to all parts and surfaces for thorough cleaning. Removable flighting screw conveyers exist in the prior art. However, those prior conveyers generally utilize some types of brackets, slots, or fittings for securing the flighting to the shaft, and in addition to providing sites for harboring food product or bacteria, they may require special tools for training on the part of the operator for disassembly and reassembly. This presents a problem where routine periodic cleaning is essential. The present invention solves these and other problems in the prior art by providing a screw conveyer having removable flighting that may be easily and quickly disassembled, thoroughly cleaned and reassembled.